Re: The toob finally sets...

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux" <jimlux-at-earthlink-dot-net> 


----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Sunday, September 12, 2004 5:18 PM
Subject: The toob finally sets...


 > Original poster: Terry Fritz <teslalist-at-twfpowerelectronics-dot-com>
 >
 > Well,
 >
 > My 19 inch Toob monitor finally blew out the blue gun, so I am using a 19
 > inch LCD now...  No more X-rays ;-))
 >
 > Plasma and LCD TV screens are still pricey, but with time...  Of course,
 > all TVs are overpriced ;o))
 >
 > Solid state Tesla coils are pushing 5 to 10 feet!!!
 >
 > Not sure if the military uses toobs in radar still...

Of course they do.. perhaps not for phased arrays (except really, really big
ones), but certainly, for the run of the mill pulsed radar with a single
feed to a reflector, a tube is hard to beat.  Tubes have the nice ability to
get very high peak powers at low duty cycles because you can jack the
voltage up "real high".

Anything where you need high peak microwave power is likely to be a tube, or
if you need high power at frequencies higher than, say, 7-8 GHz.  The Mars
Rovers use a 15W solid state amplifier for the 8 GHz X-band downlink to
Earth.  There are 100W solid state amps around, but the efficiency is much
lower than for tubes (15-20% vs 45-50%). Solid state isn't really practical
for any serious amount of power (more than a few watts) at,  32 GHz, yet.
Extended Interaction Klystrons (EIKs) are fairly common in radars at 20 GHz
and up.  For instance, there are a few cloud profiling radars running at 94
GHz that use peak powers in the kilowatt range.

One persistent advantage of tubes is that they are tough... the stray cosmic
ray or high energy particle doesn't cause ugly stuff like gate rupture.

 >
 > Only the audiophiles and microwave ovens seem to "need" toobs now ;-)))


Broadcast transmitters for FM and TV use tubes (various flavors of klystron
and TWT, typically).  AM broadcast is largely solid state, particularly for
<50kW, but some "border blaster" stations are running tubes, as are a lot of
older stations (just ran across a spec sheet on a tube for an old RCA
transmitter.. the filament was something like 270V at 40A... as a friend
says, "real tubes have handles, and come with a wheeled cart")

Gonna be a lot of years before tubes die out.  CPI (the successor to Eimac)
is still going strong...

 >
 > Cheers,
 >
 > Terry
 >
 >